11/26/18 1 Chapter 12 Introduc1on to Gene1cs 12-1 The work of Gregor Mendel • Gregor Mendel • Austrian Monk • Worked with pea plants • A. True Breeding Pea Plants – Self – pollinate and produce new plants gene1cally iden1cal to themselves – Mendel decides to cross pollinate the plants – Offspring are hybrids – Mendel studied traits • 1. seed shape • 2. seed color • 3. seed coat color • 4. Pod shape • 5. Pod Color • 6. Flower posi1on • 7. Plant height Copyright Pearson Prentice Hall Gregor Mendel’s Peas Mendel knew that •the male part of each flower produces pollen, (containing sperm). •the female part of the flower produces egg cells.
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11/26/18
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Chapter12Introduc1ontoGene1cs
12-1TheworkofGregorMendel
• GregorMendel• AustrianMonk• Workedwithpeaplants
• A.TrueBreedingPeaPlants– Self–pollinateandproducenewplantsgene1callyiden1caltothemselves
– Mendeldecidestocrosspollinatetheplants– Offspringarehybrids– Mendelstudiedtraits
• 1.seedshape• 2.seedcolor• 3.seedcoatcolor• 4.Podshape• 5.PodColor• 6.Flowerposi1on• 7.Plantheight
Copyright Pearson Prentice Hall
GregorMendel’sPeas
Mendelknewthat
• themalepartofeachflowerproducespollen,(containingsperm).
• thefemalepartoftheflowerproduceseggcells.
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Copyright Pearson Prentice Hall
GregorMendel’sPeas
Thisprocessiscalledcross-pollina1on.
Mendelwasabletoproduceseedsthathadtwodifferentparents.
Copyright Pearson Prentice Hall
GenesandDominance
Mendel’s Seven F1 Crosses on Pea Plants Mendel’s F1 Crosses on Pea Plants
! 2Conclusions! 1.Traitsarepassedfromonegenera1ontothenextbygenes
• Differentformsofgenesarecalledalleles
! 2.DominancePrinciple• Someallelesaredominantandsomeallelesarerecessive
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• B.Segrega1on– Parentplants=Pgenera1on
– Crossfer1lizeparents,theoffspringarecalledF1genera1on– WhenF1plantsflower,2allelesaresegregatedsothateachgamete(pollenoregg)hasonecopyofthatgene.
– Tt"EggT" Pollent
SUMMARY
12-2ProbabilityandPunne]Squares
! Mendelfound:! Hybridcrossedwithahybrid(Tt)createdabout¾talland¼short
! I.Gene1csandProbability" Thelikelihoodthatapar1culareventwilloccur" ThePrincipleofProbabilitycanbeusedtopredicttheoutcomeofgene1ccrosses
• II.Punne]Squares– Canbeusedtopredictandcomparethegene1cvaria1onsthatwillresultfromacross
– Homozygous:TTor]– Heterozygous:Tt
– Phenotype:physicalappearance(tall/short)– Genotype:theactualgenes(Tt/TT/])
12.3ExploringMendelianGene1csI.Independentassortment
• 2factorcross• Followingtwodifferentgenesastheypassfromonegenera1ontothenext.
• A.Twofactorcross:F1– Purebreedingplantsfor2traits– seedshapeandseedcolor
• RRYYXrryy• B.Twofactorcross:F2
– Theprincipleofindependentassortmentstate» Geneswithdifferenttraitscansegregateindependentlyduringtheforma1onofgametes
• (Dihybridcross)
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• II.SummaryofMendel’sPrinciples– 1.Characteris1csarepassedfromparentstooffspringbygenes
– 2.Someallelesaredominantandsomearerecessive
– 3.eachadulthas2copiesofagenethatseparatewhengametesareformed.
– 4.Allelesfordifferentgenesseparateindependentlyofeachother.
• III.BeyondDominantandRecessive– A.IncompleteDominance
• Onealleleisnotdominantovertheother,sowegetablendofthe2
• 4o’clockflowers• RedxWhite"Pinkfowers
– B.Codominance– Bothallelescontributetophenotype– WhitefeatherschickenXBlackfeatherschicken"Speckledfeathers
– C.Mul1plealleles– Morethan2allelesforatrait
– D.Polygenictraits– Havingmanygenes
• Morethanonegeneinvolvedinproducingthephenotype
• Skincolor
Differentcombina1onsofallelesresultinthecolorsshownhere. KEY
C = full color; dominant to all other alleles cch = chinchilla; partial defect in pigmentation; dominant to ch and c alleles ch = Himalayan; color in certain parts of the body; dominant to c allele c = albino; no color; recessive to all other alleles
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ReviewofMitosis
• Purpose–Celldivisiontoproducenewcellseverywhereinthebodyexceptforsexcells.
• Endresult:2gene1callyiden1caldaughtercells
Prophase Nuclearenvelopebreaksdown,centriolesandspindlesappear,chromosomesbecomevisible.
Metaphase Chromosomeslineupinthemiddleofthecell
Anaphase Chromosomesareseparatedintochroma1dsandpulledtooppositeendsofthecell
Telophase Nuclearenvelopere-forms,centriolesandspindlesdisappear,andcytoplasmbeginspinchingin.
Cytokinesis Celldividesinto2gene1callyiden1caldaughtercells
4 Stages of Mitosis: PMAT
12.4Meiosis
• I.ChromosomeNumber– Ex:fruitfly 8chromosomes
• Homologouschromosomes» 4chromosomesfromDad» 4chromosomesfromMom
Diploidvs. Haploid
FullsetofchromosomesEx:humans46fruitfly8
HalfsetofchromosomesEx:human23fruitfly4
• II.PhasesofMeiosis
ProphaseI Homologouschromosomespairupandformtetrads******CROSSINGOVEROCCURS**********
MetaphaseI Chromosomeslineupincenterofthecell
AnaphaseI
Chromosomesarepulledtooppositeendsofthecell
TelophaseI
Nuclearenvelopere-formsandcellsdivide.2newcells
ProphaseII
Nuclearenvelopebreaksdown,centriolesandspindleform
MetaphseII
Chromosomeslineupinthemiddle
AnaphaseII
Chromosomesarepulledapartintochroma1ds.Chroma1dsarepulledintooppositeendsofthecell.
TelophaseII Cellsdivideandproduce4gene1callydifferentcells
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• III.GameteForma1on– *Meiosisproducesgametecells
– Males–4viablespermscells– Females–1viableeggcellsand3polarbodies
• Summary
LinkageandGeneMaps
• I.GeneLinkage– Chromosomesassortindependently,notindividualgenes
• II.GeneMaps– Therela1veloca1onofeachknowngeneonachromosome
• 1.Iftwogenesareclosetogether,therecombina1onfrequencybetweenthemshouldbelow.
• 2.Iftheyarefarapart,therecombina1onfrequencyshouldbehigh.
Page280Whichwillyouhavemoreof? Purpleeyesandspeckwings orBrowneyesandspeckwings
****Browneyesandspeckwings(closertogether)*****
Summary
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